1. Field of the Invention
The present invention relates to an integrated circuit (IC) card and a data control method therefor, for communicating data with a prescribed card processing unit. Particularly, the present invention relates to an IC card having a time measuring function and a data control method for the IC card.
2. Description of the Related Art
There have been proposed and provided IC cards for communicating data with a card processing unit (for writing/reading of data) to which such an IC card is connected.
Since such IC cards have large storage capacities compared with magnetic cards, they are expected to be used for various applications in future.
The applications for which IC cards are expected to be used are for example, ID cards, ticket cards, free pass cards, commuter tickets etc.
In the prior art, IC card calculators having a time indicating function (namely, a time measuring function) have been provided.
IC cards will be utilized in future for the purposes of controlling various factors such as specified terms.
For example, if IC cards are applied to the above mentioned ID cards, ticket cards, free pass cards and commuter tickets, they are valid only within specified periods and they cannot be used after termination of the periods (and before start of the periods).
Accordingly, if an IC card is utilized for the above mentioned applications (where validity of data is limited by a time period), determination as to whether the IC card is valid or not, that is, whether the card is within a validity term or not is required each time the card is used.
If a structure for effecting such determination is provided on the side of a reading unit, data to be controlled (data of validity terms etc.) for all the IC cards to be read by the reading unit need to be stored in a memory of the reading unit.
In order to store such data, it is necessary for the memory of the reading unit to have a large capacity and consequently the reading unit becomes expensive.
For example, if an IC card is used as a commuter ticket, all terminal units for checking commuter tickets at respective stations need to be connected on-line to a host computer, which involves a considerable difficulty.